>>> "Nikolas Everett" <nik9000@xxxxxxxxx> wrote: > I'm a bit confused as to why this query writes to the disk: > SELECT count(*) > FROM bigbigtable > WHERE customerid IN (SELECT customerid FROM > smallcustomertable) > AND x != > 'special' > > AND y IS NULL > > It writes a whole bunch of data to the disk that has the tablespace where > bigbigtable lives as well as writes a little data to the main disk. It > looks like its is actually WAL logging these writes. It's probably writing hint bits to improve performance of subsequent access to the table. The issue is discussed here: http://wiki.postgresql.org/wiki/Hint_Bits -Kevin
